Carburetor



P 1949- M. CHANDLER 2,482,401

CARBURETOR Filed'July l, 1943 2 Sheds-Sheet l I N V EN TOR. MLToAr 6'.GEWDLER.

Patented Sept. 20, 1949 Milton E. Chandler, New Britain,

by mesne assignments,

Company, West Hartfor of New Jersey Conn., assignor, toNiles-Bement-lond d, Conn.,- a corporation Application July 1, 1943,Serial n uaoii 9 Claims. (Cl. 261-69) The present invention relates tocarburetors,

of fuel flowing thru the carburetor is propor tioned to the quantity ofair flowing thru the carburetor. 1

It is an object of the present invention to provide improved means forcontrolling the flow of fuel thru a carburetor in accordance with thequantity of air flowing thru it.

Another object of the present invention is to provide an improvedcarburetor of the type in which the fuel flow is controlled by a mainpressure operated valve, and'in which the operating pressure for themain valve is controlled by a pilot valve operated in accordance withthe flow of air thru the carburetor.

A further object is to provide a curburetor of the type described, inwhich the fuel, after passing thru the main valve, flows thru a meteringrestriction, and in which the pilot valve is operated not only inaccordance with the air flow thru the carburetor, but in accordance withthe fuel pressure on the downstream side of the metering restriction. t

Another object of the present invention is to provide an improved pilotvalve for a carburetor of the type described.

A further object is to provide improved mech anism for operating a valvein accordance with the resultant of a plurality of variable pressures,in which each of the variable pressures is transmitted to one of aplurality of expansible cham-. bers which are separated by flexiblediaphragms.

A still further object is to provide, in such a device, improved meansfor transmitting the forces on the flexible diaphragms to the valve.

Other objects and advantages of my invention will become apparent froma, consideration of the appended specification, claims, and drawing, inwhich Figure 1 is a somewhat diagrammatic illustration of a carburetorand fuel supply system for an internal combustion engine embodying theprinciples of my invention,

Figure 2 illustrates a modified form of pilot valve which may be used inthe carburetor of Figure 1, and 7 Figures 3 and 4 illustratebthermodified forms of pilot valves which-may be used in the carburetor ofFigure 1..

Referring now to Figure 1, there is shown a carburetor having a mainbody l0, through which extends a main air passage I l,- between an inletl2 and an outlet l3; Although any suitable typ of carburetor may beused, I prefer to use one of the rectangular type shown and claimed inmy copending application, Serial No. 406,776, filed August 14, 1941, nowPatent No. 2,36 ,993, issued Nov. 7, 1944.

Air flowing through the passage H flows from the inlet l2 pastaplurality of parallel ,Venturi members 14, and past a pair of throttlesl5 and a discharge nozzle I6 to the outlet I3; The flow of air throughthe passage- H is controlled by the throttles I5, and the flow of air ismeasured by a Venturi metering. arrangement including the Venturimembers 1 f A plurality'of impact tubes I! extend into the inlet portion12 of thepassage H, with their open ends exposed to the flowing air. Theimpact tubes l'l 'communicate'with a passage l8, commonly termed a'ventring.

Each of the hollow Venturi members I4 is provided with a plurality oflateral openings 20, which openings connect the hollow interiors of theVenturi members I4 with the air passage H at or near its narrowestportion. It will be rec'- ognized that, in accordance with the knownprinciples of Venturi meters, the difference between the pressureexisting at theimpact tubes l1 and that existing at the openings 20 inthe throat of the venturi, is a measure of the velocity of air flowingthrough passage I I.

In order to secure proper combustion of the fluel flowing through thecarburetor, the mass of fuel flowing per unit time should beproportioned to the mass of air flowing (per unit time), rather than tothe velocity of the flowing air. If the air were of constant density,its velocity could be taken as a measure of the mass of air flowing perunit time through passage I l. 'I-Iowever, since the density of the airvaries with atmospheric pressure and temperature, the pressuredifferential produced by the Venturi structure must be corrected toobtain a pressure differential which is a true indication of the mass ofair flowing through the carburetor.

A 'portionof the air sage enters the impact tubes I'L. From there itpasses through; a secondair passage, paralleling a portion of the mainair passage I l, and including ventring 18, a conduit 2l ,a conduit 22having a restriction 23 therein, a'conduit 24, a valve chamber 25, and aconduit 26 to the interior of the two central hollowVenturimembers [4,;and out through the openings 20 in those members 'to the main airpassage ll. Y

A valve 21, located in the valve chamber 25, controls the flow of airthrough this second pasflowing through the passage. The valve 27 isbiased by a spring 3| into engagement with a flexible bellows 28, whichis exposed on one side to the pressure in the chamber 25, and on itsother side to the pressure in a chamber 32 formed between the bellows 28and a rigid casing 30. The chamber 32- is filled with nitrogen or othersuitable' fluid, so that the volume of the chamber 32 varies with thetemperature and pressure of the fluid surrounding it. If the density ofthe flowing air decreases, due either to a decrease in atmosphericpressure such as might be occasioned by an increase in altitude of anaircraft or due to an increase in temperature, the chamber 32 expands,thereby moving the valve member 21 to the right and decreasing the airflow through the second passage previously described. The valve 21 maybe so designed'and proportioned with respect to restriction 23; inconduit 22, that the pressure difierential across the restriction 23 isalways an accurate measurement of the mass of air flowing through themain air passage regardless of the variations in. the density in theair.

The exterior of the casing 38 is exposed to the air within a chamber 33formed in the carburetor body [8. In order to maintain the temperatureof the air in the chamber 33 at the same temperature ast'he air passingthru the passage H, the chamber 83 is connected through a conduit 34 tothe 'interiors'of two outer Venturi members 54, which are not used forair flow measurement purposes. Another portion of the chamber '33. isopen to, the passage H, as at 35, somewhat downstream from the Venturimembers l4. A pressure differential is thereby created which causes acontinuous flow of air around the outside of casing 38, thereby insuringthat the fluid within the casing is maintained at thesame temperatureas'the airflowing. through the careburetor. This condition is furtheraided by a projection 35 on the casing 38, which extends through theopening 35 a substantial, distance into the air pas' sage The fuelflowing through the carburetor is re; ceived from a fuel pump or othersource of fuel unde superatmospheric pressure (not shown), and'pas'sesthrough a' vapor trap 40, a conduit 4|, amain fuel regulator valve unit42, a conduit. 43, a mixture control valve 44, a jet system 45, aconduit 46, a pressureregulator valve 4], anda conduit 48 tothedisoharge nozzle l6.

The vapor trap 40 includes a screen 68, which prevents'the passage offoreign materials therethrough. A valve 6| .is located at the top of thevapor trap casing and is operated by'float 82, so that when the levelofthe fuel in the vapor trap falls because of; the formation of vaportherein, the valve 6| is opened, allowingthe vapor to escape throughaconduit 63 which may be con nected to, the fuel tank or to anothersuitable place for the disposition of the vapor. A ring 64 surrounds aported sleeve 65, through which the valve 6| moves. The ring 65isprovided so that if the aircraft is flown upside down, it slides downover the ports in the sleeve 65, preventing the drainage of fuel fromthe vapor trap through the valve 6|.

The mainlfuel regulator valve unit 42 includes a valve member 66 carriedby a stem 61, which is attached by any suitable means to the centralportion of a flexiblediaphragm 68, which is attached at its edges to theoasingof the'regulator unit 42, so as to divide the easing: into a pairof expansiblechambers '|0 and 5|. The valve member 68 cooperates with aseat formed in the 4 casing of the regulator unit 42. A spring 12,located within the chamber 5| biases the valve member 65 toward openposition. The position of valve member 66 is determined by thedifierence between the pressure in the chamber I0, which acts to closethe valve, and the pressure in the chamber 5|, aided bythe spring 12,both of which act to open the valve. The pressure in the chamber 5| isregulated by the pilot valve unit 54 in a manner more completelydescribed below.

The mixture control valve 44 includes a manually operable. shaft 13,carrying a disc valve 14. The disc valve 14 controls the flow of fuelthru a pair of conduits 15 and 16 extending from the mixture controlunit 44 to the jet system 45. The disc valve 14 is usually positioned sothat either conduit 76 alone is open, both conduits are open, or bothare closed. When the conduit 76 alone is open, the carburetor is said tobe operating with an automatic lean mixture, and when both conduits l5and 18 are open, the carburetor is said to be operating with anautomatic rich mixture. 1

When the conduit 'Hiis open, fuel flows to the carburetor through afixed jet H, and upon the occurrence of a predetermined high pressuredifferential across the jet system 45, a spring loaded valve opensanother jet 18, When the conduit 15 is also opened, a third jet 8| isopened. The maximum flow of fuel through the jets l8 and 8| isrestricted by another jet 82. The jet system 45 is quite conventional oncarburetors of the type described It will be understood that thequantity of fuel flowing thtQ lgh the jet system 45 for a give nposition of the mixture control valve 44, is a function of the pressuredifferential across the jet system.

The pilot valve unit 54 includes a casing 83 whose interior, is dividedby three flexible diaphragms 84, 8 5 and 86 into four expansiblechambers 81, 88, 90 and55. The chamber 81 is connected througha conduit9| to the conduit 58, andhence the pressure in the chamber 81 is thesame as, or at least indicative of, the pressure on the dischargesideof. the jet system 45. Thechamber 881s connectedthrough a conduit 92and the conduit 2| to the vent ring I8, so that thepr essure in cham ber88 is indicative of the pressurein the inlet |2- of the air passageThechamber 98 is connected through the conduit 83 to the downstream sideof the restriction 23 in conduitZZ. Therefore, the. pressuredifferential betweenchambers 88 and QO is a measure of the. mass'of airflowing to the carburetor.

A valve member $14 is carriedcentrally of the diaphragm 86, andcooperates with a seat 95 attachedto the casing 83 by any suitablemeans. The chamber 55 in which the valve member 54 is located, isconnected through the conduit 52 with the chamber 5| in the mainregulator valve 42. The chamber 53, which receives the fluid dischargedthrough the valve 84, empties into the conduit 58 through a0017111111556: having a restriction 51 therein.

A force transmitting member 96, having a convex. upper surface, isattached to the, central part of diaphragm by any suitable means.Another force transmitting member 91; having 7 a fiat lower surface isattached to the central portion of the diaphragm 85. By reason. of theconvex surface in the member 98' andthe flat surface on the member illithe two members may engage each otherjfor the transmission of forcesfrom onej'member tothe other, without any lateral binding action betweenthem, regardless of relative lateral displacement of the diaphragms i 85and 86. The upper surface of the member 91 is provided with a centralrecess adapted to receive a projection 98 on the lower surface of aforce transmitting member 99 attached to the central portion ofdiaphragm 81. The force transmitting member 99 is likewise provided witha recess in the central portion of its upper. surface, which recess isadapted to receive a guiding projection I90 on a plug IOI which isthreadedly mounted in an aperture in the casing 83. The projections 98and I 08, and the recesses with which they cooperate maintain theforce'transmitting members 91 and 99 in a central position in the casing83. It will be noticed that the projection 98 is slightly smaller indiameter than the recess in which it moves so as to permit relativelateral movement between the diaphragms 84 and 85. M

A tension spring I02 extends between the valve member 94 and a nut I03threadedly mounted on a bolt I84 extending through the bottom of thecasing 83. The bolt I04 is provided with a hexagonal head I05 by whichit may be adjusted to vary the tension of the spring I02. A lock nut I99is provided to fix the bolt I04 so as to maintain any adjustmentestablished for the tension of spring I92.

The pressure in the chamber 81 is maintained at a value greater thanatmospheric pressure, by the fuel pump or other similar means. Thepressure in chamber 88 is always equal to atmospheric pressure, sincethat chamber is connected to the vent ring I8. Therefore, thedifferential pressure acting on the diaphragm 84 tends to move thatdiaphragm downwardly, and maintains the force transmitting member 99 inengagement with the member 91 attached to'diaphragm 85.

In a similar manner, it will be seen that the pressure in chamber 90 isalways less than that in chamber 88, since it is established by thesuction at the throat of the venturi. The force acting on diaphragm 85is, therefore, downward.

The pressure in the chamber 55 is larger than the pressures in any ofthe other three chambers, since it is connected to the upstream side ofjet system through the conduit 52 and restriction 50. Therefore, thepressure below the diaphragm 88 is higher than the pressure above it,and-the force actin on diaphragm 86 is upward, tending to maintain themember 96 in engagement with member 91.

The force acting on diaphragm 86, therefore, tends to open the valve 94,while the forces acting on diaphragms 84 and 85 tend toclose the valve94. These latter two forces are aided bythe tension of spring I82. Asthe valve 94 moves towards its open position, the pressure in chamber'55is released, thereby decreasing the force tending to move the valvetoward open position. Likewise as the valve 94 moves towards its closedposition the pressure in chamber is increased thereby building up anopposing force tending to stop the motion of the valve. It may,therefore, be seen that the valve 94 is positioned so as to regulate thepressure in the chamber 55 in accordance with the resultant of thepressures in the chambers 81, 88, and 90.

As previously described, the differential between the pressures in thechambers 88 and 90 of the pilot valve unit 54 is a measure of the massof air flowing per unit time thru the passage II. This pressuredifferential produces a force acting downwardly on diaphragm 85 which islikewise a measure ofthe mass of air flowing per unit time.

The pressure in chamber 55 is indicative ofthe: pressure in the fuellineon the upstream side of the jet system. The pressure in chamber 81 isindicative of the pressure in the fuel line on the downstream-side ofvthe jet system. The differential between these two fuel pressuresprovides a force acting upwardly on the valve 94. The air pressuredifferential acting on diaphragm acts in a direction to close valve 94and the fuel pressure differential acts to open valve 94. Closure ofvalve 94 results in an increase in pressure in chamber 55 which istransmitted thru conduit 52 to chamber 5| and acts on diaphragm 68 tomove valve 85 in an opening direction. It may, there-- fore, be statedthat the air pressure differential acts on the pilot valve94 in 'a fuelflow increasing direction, the fuel flow referred to being the flow thruthe main fuel line. Conversely, the fuel pres-- sure differential actson the pilot valve 94 in a fuel flow decreasingdirection. The pilotvalve unit balances the air pressure differential against the fuelpressure differential and corrects the fuel flow to regain a conditionof balance in case the two pressure differentials become unbalanced.

A pilot valve unit 54 is formed from an upper casting 89 and a lowercasting 83. In assembling thisunit, the diaphragm 86 has its edgesattached to casting 83 by the bolts between upper and lower plates asshown in the drawing, so that the chamber 55 is formed under thediaphragm 86 between the diaphragm and the lower plate. In a similarmanner the diaphragm 84 is clamped to the upper casting 89, forming withthe central recess in that casting the chamber 81. The two castings arethen placed together, clamping the edges of the diaphragm 85 betweenthem and are then fastened in that position. This completes thestructure of the four chambers of the pilot valve unit. It should benoted that the diaphragms carry the force-transmitting members 96, 91and 99 at their centers, so that the mechanism for transmittin theforces to the valve is completed by the act of assembling the diaphragmsand the two castings of the housing.

The regulator valve 41 is attached to adiaphragm I II], which is exposedon one side to the inlet pressure of the fuel flowing thru the valve 41and on its opposite side to the pressure in a chamber I connectedthrough a conduit H2 to the vent ring I8. A spring II3 aids the pressurein the chamber I I I in balancing the force due to the pressure on theopposite side of diaphragm H0. The function of the regulator valve 41 isto maintain a substantially constant pressure inside the dischargenozzle I6, so that the fuel flow through the discharge nozzle will notbe affected by variations in the pressure in the air passage I Idownstream from the throttles I5.

An idling valve I I4 is located in the conduit 48 between the jet system45 and the regulator valve' 41. The idling valve H4 is connected by alinkage, (not shown), to the throttles l5, so that when the throttlesare moved toward their closed positions the idling valve H4 is movedtowards its closed position to decrease the fuel flow therethrough. In acarburetor of the type described, the differential pressure in thechambers 88 and 99 is so small at low air flows that it exerts noappreciable controlling effect on the fuel flow.

The spring I02 acts on the valve 94 in a closing.

direction. As previously pointed out, movement of valve 94 towardsclosed position tends to cause an opening movement of valve 86 and aconsequent increase in fuel'flowr The spring 12 directly biases thevalve 68 in a fuel flow increasing art and I therefore intend that myinvention shall be limited only by the appended claims.

I claim as my invention:

1. A carburetor for an internal combustion engine, comprising incombination, a first conduit for conveying air for combustion purposesto said engine, metering means in said first conduit for producing twounequal pressures therein whose difference is a measure of thequantityof air flowing therethru, a, source of fluid fuel under superatmosphericpressure, a second conduit for conveying fuel from said source to saidengine, a metering restriction in said second conduit, means forregulating the fuel pressure in said second conduit at the dischargeside of said restriction, first valve means for controlling the fuelpressure on the intake side of said restriction and thereby controllingthe flow of fuel therethru, means for operating said first valve meansincluding a third conduit for by-passing fuel from said source aroundsaid restriction to said fuel pressure regulating means, said thirdconduit including a restriction, an expansible chamber having a movablewall attached to said first valve means for positioning the same, andsecond valve means for controlling the flow of fluid thru said thirdconduit and thereby the pressure in said chamber and the position ofsaid first valve means, said second valve means comprising a seat memberhaving a port therein, a valve member movable with respect to said seatmember to open and close said port, a housing, at least three flexiblepartitions extending transversely of said housing to provide fourexpansible chambers in said housing, sleeve means attached to all saidpartitions and carrying one of said members so that said one member ispositioned in accordance with the resultant of the forces acting on saidpartitions, means for supplying to two of said chambers fluid under saidtwo unequal pressures so that an increase in the difference between saidtwo pressures tends to cause a closing movement of said valve member,means connecting a third of said chambersto said second conduit at thedischarge side of said restriction, means connecting the fourth of saidchambers to said third conduit so that the difference between thepressures in said third and fourth chambers tends to cause an openingmovement of said valve member, and a passage thru said sleeve meansconnecting said third and fourth chambers and controlled by said valveand seat members, said passage, said third and fourth chambers and theirassociatedconnecting means forming a portion of said third conduit.

' 2. A carburetor for an internal combustion engine, comprising incombination, a first conduit for conveying air for combustion purposesto said engine, metering means in said first conduit for producing twounequal pressures therein whose difference is a measure of the quantityof air flowing therethru, a source of fluid fuel under superatmosphericpressure, a second conduit for conveying fuel from said source'to saidengine, a metering restriction in said second conduit, means forregulating the fuel pressure in said second conduit at the dischargeside of said restriction, first valve means for controlling the fuelpressure on the intake side of said restriction and thereby controllingthe flow of fuel therethru, means for operating said first valve meansincluding a third conduit for by-passing fuel from said source aroundsaid restriction to said fuel pressure regulating means, saidthirdiconduit including a restriction, an expansible chamber having amovable wall attached to said first valve means for positioning thesame, and second valve means for controlling the flow of fluid thru saidthird conduit and thereby the pressure in said chamber and the positionof said first valve means, said second valve means comprising a seatmember, a valve member movable with respect to said seat member, ahousing for said members, at least three flexible partitions extendingtransversely of said housing to provide four eXpansible chambers in saidhousing, means for transmitting the forces acting on said flexiblepartitions to at least one of said members to control the relativepositions of said members, means for supplying to two of said fourchambers fluid under said two unequal pressures so that an increase inthe difference between said two pressures tends to cause a closingmovement of said valve member, means connecting a third of said fourchambers to said pressure regulating means, and means connecting thefourth of said four chambers to said third conduit so that'thedifference between the pressures in said third and'fourth chambers tendsto cause an opening movement of said valve member, said third and fourthchambers being adjacent each other and interconnected by said valve andseat members, and forming therewith a portion of said third conduit.

3. A carburetor for an internal combustion engine, comprising incombination, a first conduit for-conveying air for combustion purposesto said engine, metering means in said first conduit for producing two,unequal pressures therein whose dliference is a measure of the quantityof air flowing therethru, a source of fluid fuel under superatmosphericpressure, a second conduit for conveying fuel from said source to saidengine, a metering restriction insaid second conduit, means forregulating, the fuel pressure in said second conduit at the dischargeside of said restriction, first valve means for controlling the fuelpressure on the intake side of said restriction and thereby controllingthe flow of fuel therethru, means for operating said first valve meansincluding a third conduit for toy-passing fuel from said source aroundsaid restriction to said fuel pressure regulating means, said thirdconduit including a restriction, an expansible chamber having a movablewall attached to said first valve means for positioning the same, andsecond valve means for controlling the flow of fluid thru said .thirdconduit and thereby the pressure in said chamber and the position ofsaid first valve means, said second valve means comprising a seatmember, a valvemember movable with respect to said seat member, ahousing for said members, at least three flexible partitions extendingtransversely of said housing to provide four expansi-ble chambers insaid housing, means for transmitting the forces acting on said flexiblepartitions to at least one of said members to control the relativepositions of said members, means for supplying to two of said fourchambers fluid under saidtwo pressures so that an increase in thedifference between said two pressures tends to cause a closing movementof said valve member, means connecting a third of said four chambers tosaid pressure regulating means, and means connecting the fourthof saidfour chambers to said third conduit so that an increase in thedifference between the pressures in said third and fourth chambers tendsto cause an opening movement-of said valve member, said members '11controlling a passage interconnecting said third and fourth chambers,and forming with said third and fourth chambers a portion of said thirdconduit.

4. A carburetor for an internal combustion engine, comprising incombination, a first conduit for conveying air for combustion purposesto said engine, metering means T'm said first conduit for producing twounequal pressures therein whose difference is a measure of the quantityof air flowing therethru, a source of fluid fuel under superatmosphericpressure, a second conduit for conveying fuel from said source to saidengine, a metering restriction in said second conduit, means forregulating the fuel pressure in said second conduit at the dischargeside of said restriction, first valve means for controlling the fuelpressure on the intake side of said restriction and thereby controllingthe flow of fuel therethru, means for operating said first valve meansincluding a third conduit for by-passing fuel from said source aroundsaid restriction to said fuel pressure regulating means, said thirdconduit including a restriction, an expansible chamber having a movablewall attached to said first valve means for positioning the same, andsecond valve means for controlling the flow of fluid thru said thirdconduit and thereby the pressure in said chamber and the position ofsaid first valve said second valve means comprising a seat member, avalve member movable with respect to said seat member, a housing, atleast three flexible par-titions extending transversely of said housingto provide four expansible chambers in said housing, means fortransmitting the forces acting on said flexible partitions to at leastone of said members to control the relative positions of said members,stop means for limiting the opening movement of said valve member withrespect to said seat member, means for supplying to two of said fourchambers fluid under said two unequal pressures so that an increase inthe difference between said two pressures tends to cause a closingmovement of said valve member, means con necting a third of said "fourchambers to said pressure regulating means, and means connecting thefourth of said four chambers to said third conduit so that an increasein the d iiference between the pressures in said third and fourthchambers tends to cause an opening movement of said valve member, saidmembers controlling a passage interconnecting said third and fourthchambers, and forming with said third and fourth chambers a portion ofsaid third conduit.

'5. A carburetor for an internal combustion engine, comprising incombination, a first conduit for conveying air for combustion purposesto said engine, metering means in said first conduit for producing twounequal pressin s therein whose diiference is a measure of the quantityof air flowing therethru, a source of fluid fuel under superatmosphericpressure, a second conduit for conveying fuel from said source to saidengine, a metering restriction in said second conduit, means forregulating the fuel pressure in said second conduit at the dischargeside of said restriction, first valve means for cmitrolling the fuelpressure on the intake side of said restriction and thereby controllingthe how of fuel therethru, means for operating said first valve meansincluding a third conduit for by-passing fuel from said source aroundsaid restriction to said fuel pressure regulating means, said thirdconduit including a restriction, an expansible chamber hav- 'ing amovable wall attached to said first valve means for positioning thesame, and second valve means for controlling the flow of fluid thru saidthird conduit and thereby the pressure in said chamber and the positionof said first valve means, said second valve means comprising a housing,at least three flexible partitions extending transversely of saidhousing to provide four expansible chambers therein, sleeve meansattached to all said partitions and having a passage therethruinterconnecting the chambers at the opposite ends of said housing, avalve member carried by said sleeve means'at one end thereof, a seatmember attached to said housing for cooperation with said valve memberto control the flow of fluid thru said passage, mounting means for saidseat member comprising a post extending thru said passage for guidingthe movements of said sleeve means, means for supplying to two of saidchambers fluid under said two unequal pressures so that an increase inthe difierenoe between said two pressures tends to cause a closingmovement of said valve member, means connecting a third of said chambersto said second conduit at the discharge side of said restriction, andmeans connecting the fourth of said chambers to said third conduit sothat the difference between the pressures in said third and fourthchambers tends to cause opening movement of said valve memher, saidpassage connecting said third and fourth chambers and forming therewith.a portion of said third conduit.

6. A carburetor for an internal combustion engins, comprising incombination, a first conduit for conveying air for combustion purposesto said engine, metering means in said first conduit for producing twounequal pressures therein whose difference is a measure of the quantityof air flowing therethru, a source of fluid fuel under superatmospheri-cpressure, a second conduit for'conveying fuel from said source to saidengine, a metering restriction in said second confrom said source aroundsaid restriction to said fuel pressure regulating means, said thirdconduit including a restriction, an expansible chamber having a movablewall attached to said valve means for positioning the same, and secondvalve means for controlling the flow of fluid thru said third conduitand thereby the pressure .in said chamber and the position of said firstvalve means, said second valve means comprising a seat memher having aport therein, a valve member movable with respect to said seat member toopen and close said port, a housing, at least three flexible partitionsextending transversely of said housing to provide four 'expans-iblechambers in said housing, means for transmitting the forces acting onsaid flexible partitions to at least one of :said members to control therelative positions of said members, means for supplying to two of saidfour chambers fluid under said two unequal air pressures so that anincrease in the difierence between said two pressures tends to cause aclosing movement of said valve member, means connecting a third of saidfour "chambers to said pressure regulating means, and means connectingthe fourth :of said vfour 'ol'rambers to said third conduit so that anincrease in the difference between the pressures in said third andfourth chambers tends to cause an opening movement of said valve member.

7. Fuel and air proportioning apparatus for an internal combustionengine, comprising a conduit for combustion air flowing to said engine,means associated with said conduit for producing two unequal pressureswhose difference is a measure of the rate of flow of air thru saidconduit, a conduit for fuel flowing to said engine, a meteringrestriction in said fuel conduit for regulating the flow of fueltherethru in accordance with the fuel pressure differential establishedthereacross, means for maintaining a substantially constant pressure insaid fuel conduit on the downstream side of said restriction, and meansfor controlling the pressure on the upstream side of said restrictionincluding a valve, an expansible chamber having a movable wall subjecton its external surface to the pressure controlled by said valve, arestricted inlet passage for admitting fuel to said chamber from thefuel conduit on the upstream side of said restriction, a restrictedoutlet passage for discharging fuel from said chamber to saidfuelconduit at the downstream side of said restriction, and pilot valvemeans responsive to the difference of said two unequal air pressures forvarying the crosssectional area of one of said restricted passages.

8. Apparatus for positioning a valve to be operated in accordance withthe resultant of four variable pressures, comprising a generallycylindrical housing, three parallel flexible diaphragms extendingtransversely of said housing and separating said housing into fourexpansible chambers, three separately movable, rigid force-transmittingmembers, one mounted substantially centrally of each of said diaphragms,first guide .means including cooperating guide elements on one end ofsaid housing and on the force-trans- :mitting member on the diaphragmnearest said one end, second guide means including cooperating guideelements on the other end of said housing and on the force-transmittingmember on the diaphragm nearest said other end, third guide meansincluding cooperating guide elements on the force-transmitting member ofthe center one of said diaphragms and on the force-transmitting memberof one of the adjacent diaphragms, cooperating surfaces on theforce-transmitting member on said center diaphragm and on theforce-transmitting member on the other adjacent diaphragm, one of saidsurfaces being rounded and the other flat to permit relative lateralmovements of said center diaphragm and said other adjacent diaphragm andto transmit only forces acting normal to the point of contact of saidsurfaces, means directly connecting one of said diaphragms to saidvalve, and means for supplying each of said four chambers with a fluidunder one of said four variable pressures, so as to apply to each of thediaphragms not directly connected to the valve a force acting towardsaid directly connected diaphragm and thereby to hold 14 said members inengagement with one another and to operate said valve in accordance withthe resultant of said pressures.

9. Apparatus for positioning a valve to be operated in accordance withthe resultant of four variable pressures, comprising a pair ofcomplementary housing members, each housing member having a firstgenerally cylindrical recess in one face thereof and a second generallycylindrical recess of smaller diameter at the bottom of said firstrecess, a valve seat in one of said second recesses, three diaphragmunits, each unit comprising a. flexible diaphragm and a rigidforcetransmitting member mounted substantially at the'center thereof,means for clamping the periphery of the diaphragms of two of said unitsto the edges of said second recesses in said two housing members so thatsaid two units with their associated recesses form expansible chambers,a valve carried by the one of said two units adjacent said valve seatfor cooperation with said seat, the third of said units being adapted tohave its periphery clamped between the edges of said first recesses whensaid housing members are fastened together, so that said third unitforms with said first recesses two more expansible chambers, each pairof adjacent force-transmitting members having cooperating surfaces whichpermit relative lateral movements of said members, said units includingall the force-transmitting mechanism between said diaphragms, so thatsaid members are assembled in force-transmitting relation by theassembling of said units and said housing members, means for supplyingto each said chamber a fluid under one of said variable pressures, sothat, for each of said units except the one carrying said valve, thepressure on the side farthest from said valve is greater than thepressure on the side nearest said valve, each said force-transmittingmember being moved toward said valve by the pressure differential actingon its associated diaphragm, so that said force-transmitting members arestressed in compression and said cooperating surfaces are maintained incontact to position said valve in accordance with the resultant of thepressures in all said chambers. MILTON E. CHANDLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS-

